There are two types of endocytosis: pinocytosis and phagocytosis. The viral membrane fuses with the cellular membrane, forcing the DNA into the host cell. Viruses enter the cell by a different mode of bulk transport. In some cases, enzymes may digest the molecules transported into the cell by endocytosis. In endocytosis, the cellular membrane folds around the materials being transported to form vesicles that move from one side to the other.
Some materials are moved across cell membranes through the processes of endocytosis or exocytosis. The protein recognizes the molecule or ion to be transported and passes it through its transmembrane domain. They usually have one or more transmembrane domains that cross through the membrane lipid bilayer, as well as domains that bind with ligands inside and outside of the membrane.
Transmembrane proteins are proteins that cross a cell membrane. Hydrogen pumps build up an electrochemical gradient of H+ ions in cells to power cellular respiration. For example, sodium ions are transported across the plasma membrane, and the electrochemical gradient powers active transport of another ion or molecule. This potential can provide energy for metabolism. Electrochemical potential is built up by pumping ions into or out of the cell. Secondary active transport, or coupled transport, is not coupled to ATP. It uses the energy of photons to move protons across the thylakoid membrane of the chloroplast, creating redox potential. Photosynthesis is also based on active transport. This generates energy used to power life. It moves protons across the mitochondrial membrane from lower to higher concentration. Combination therapy shows promise for treating triple-negative breast cancerĪnother important example of active transport is the mitochondrial electron transport chain, which is based on reduction of NADH.Drugs that block mineralocorticoid receptor may help protect bone cells during aging.